The present invention relates generally to video compression, and more particularly, to decoding where the number of transform coefficients in B-frames are reduced in order to reduce the computational complexity of the decoding.
Video compression incorporating a discrete cosine transform (DCT) is a technology that has been adopted in multiple international standards such as MPEG-1, MPEG-2, MPEG-4, and H.262. Among these schemes, MPEG-2 is the most widely used, in DVD, satellite DTV broadcast, and the U.S. ATSC standard for digital television.
An example of a MPEG video decoder is shown in FIG. 1. The MPEG video decoder is a significant part of MPEG-based consumer video products. In such products, one design goal is to minimize the complexity of the decoder while maintaining the video quality. In order to achieve this goal, an adaptive scheme has been used to either fully perform or skip completely a discrete cosine transform (IDCT) computation of B-frames.
The above-mentioned adaptive scheme is based on a simple DC coefficient test. If the DC coefficient of a DCT block is larger than a threshold, the full IDCT is computed. Otherwise, the computation of the IDCT is skipped, which provides computational savings. However, a problem in this method is that simple threshold test cannot always accurately determine the sparseness of the test. Therefore, the decoded video output quality is not always good and the computations required in testing the DC coefficient in a media processor may take quite a few CPU cycles.